Ashley Hendricks, a University of Alabama student from Huntsville, holds a sign and chants while protesting HB-56 on Sept. 28, 2011. / Robert Sutton, AP

by Richard Wolf, USA TODAY

by Richard Wolf, USA TODAY

WASHINGTON -- The Supreme Court has let stand a lower court's decision blocking states from prosecuting people who harbor or transport undocumented immigrants.

Similar provisions already exist in federal law, but many states have passed their own, tougher immigration laws and take immigration matters into their own hands.

By refusing to reconsider the case, the high court will let stand a federal appeals court's ruling last year that went against Alabama. That law garnered attention for another provision, thrown out by an appeals court, that targeted public school students in the country illegally.

Justice Antonin Scalia dissented from the Supreme Court's decision not to consider the case. It takes four justices to put a case on the high court's docket.

The appeals court's decision had upheld other parts of the Alabama law, including one that allowed police to check people's immigration documents when stopped for other purposes. A similar provision in Arizona was upheld by the court last year.